One day, Umar bin Ubaid, who was considered the leader of Mutazila sect asked Imam Muhammad Baqir (a.s), “What is the meaning of the verse:
Do not those who disbelieve see that the heavens and the earth were closed up, but We have opened them. (Surah Anbiya 21:30)
Imam replied, “The sky was closed, means not a drop fell from the sky to the earth and the earth was closed means, no vegetation grew up from it. When Allah accepted the prayers of Adam (a.s) the earth burst forth and streams began to flow, trees grew and began to fructify. Rain fell from the sky. Thus this is the meaning of “closed up” and “We opened them”.
Once Tawus Yemeni asked Imam (a.s), “When did one-third of Adam die?” Imam replied, “It never happened so. Rather you should ask when did one-fourth of human population die? It was when Habeel killed Qabeel. At that time there were four human beings, Adam, Hawwa, Habeel and Qabeel. Thus by the slaying of Qabeel, one-fourth of the population decreased.”
Tawus Yemeni asked, “What is that, which is permitted in small quantity but prohibited in large measure. Imam (a.s) replied, “It was the stream of Talut, drinking more water from it was not allowed, only a handful was permitted.”
Then he asked, “Which fast was it, when it was allowed to eat and drink?” “It was the vow of silence that Maryam (a.s) had observed,” replied the Imam (a.s). That is she did not speak to anyone in this fast.
Tawus asked, “What is that goes on decreasing and never increases?”
“Life,” replied Imam (a.s).
“What is that which goes on increasing and never decreased?”
“The sea,” replied the Imam (a.s).
Then he asked, “What is that, which became airborne only once?”
“Mt. Tur, which rose up and hovered on the heads of Bani Israel,” said the Imam (a.s).
He asked, “Who are those people who gave a true testimony that Allah considered false?”
“It was the testimony of the hypocrites regarding the prophethood of Allah’s Messenger, but Allah considered it false.”
It means that what they had stated was correct but their statements were considered false because they did not testify with sincerity, they only claimed so verbally.
Reference :Akhlaq al-A’imma, Morals & Manners of the Holy Imams